From: Pavel Emelyanov <xemul@parallels•com>
To: "Eric W. Biederman" <ebiederm@xmission•com>
Cc: Linux Netdev List <netdev@vger•kernel.org>,
David Miller <davem@davemloft•net>
Subject: Re: [PATCH 1/2] net: Allow to create links with given ifindex
Date: Tue, 31 Jul 2012 17:30:17 +0400 [thread overview]
Message-ID: <5017DDE9.4020008@parallels.com> (raw)
In-Reply-To: <878ve0dtw3.fsf@xmission.com>
>> First, let's imagine that on host A the loopback device got registered as
>> first device, but on host B for some reason some other device got registered
>> first. In that case after migration from A to B the lo on B will have index
>> equals 2. And there's no any strict requirement that lo's per net operations
>> are registered first. Please, correct me if I'm wrong.
>
> Actually there is a hard requirement that the loopback device be the
> last device in a network namespace to be unregistered. We meet that
> requirement by registering the loopback device first
> "net/core/dev.c:net_dev_init()".
Hm... Indeed, and this is good news!
>> Next. In fact, lo is not the only problem. Look at the e.g. sit versus ipgre
>> fallback devices. Both gets created on netns creation and obtain whatever
>> ifindices are generated for them. Even if we make ifidex per netns chances
>> that sit gets registered _strictly_ before ipgre equal zero, since they are
>> both modules.
>
> True. However those fallback devices should no longer be needed,
> and even if they are I think you can delete and recreate them.
Good idea! I will look at that direction.
> Making lo the particularly interesting case.
Yup, provided we can manually recreate those auto-created devices this solves
the issue.
>> Just an idea -- is it worth moving the possibility to have ifindidces intersect
>> under CONFIG_<SOMETHING> (EXPERT/CHECKPOINT_RESTORE) to let wider audience check
>> the code in real-life?
>
> I think the best testing we are going to get diversity wise is to create
> a per netns counter into dev_new_index when net-next opens up.
>
> Having an ifindex that we can only set at netdevice creation time seems
> reasonable.
OK, thank you, Eric.
> Eric
> .
>
Thanks,
Pavel
next prev parent reply other threads:[~2012-07-31 13:30 UTC|newest]
Thread overview: 19+ messages / expand[flat|nested] mbox.gz Atom feed top
2012-07-30 4:34 [PATCH 1/2] net: Allow to create links with given ifindex Pavel Emelyanov
2012-07-30 4:36 ` [PATCH 2/2] veth: Allow to create peer link " Pavel Emelyanov
2012-07-30 10:49 ` [PATCH 1/2] net: Allow to create links " Eric W. Biederman
2012-07-30 10:56 ` Eric W. Biederman
2012-07-31 9:03 ` Pavel Emelyanov
2012-07-31 11:58 ` Eric W. Biederman
2012-07-31 13:30 ` Pavel Emelyanov [this message]
2012-08-02 10:28 ` Eric Dumazet
2012-08-02 11:09 ` Eric W. Biederman
2012-08-02 23:37 ` David Miller
2012-08-02 23:26 ` David Miller
2012-08-03 5:45 ` Eric Dumazet
2012-08-03 5:51 ` Eric Dumazet
2012-08-03 23:56 ` David Miller
2012-08-04 7:10 ` Eric Dumazet
2012-08-04 8:25 ` David Miller
2012-07-30 11:51 ` Eric Dumazet
2012-07-30 12:33 ` Eric W. Biederman
2012-07-31 9:06 ` Pavel Emelyanov
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